PLASTIC CONDUITS IN ELECTRICAL INSTALLATIONS

The electrical engineer using metal conduits is faced with a dual menace from corrosion—external and internal. With steel conduits especially, dampness, corrosive atmospheres, or actual contact with chemical substances result in severe rusting, leading not only to the eventual destruction of the conduits but also—and this is probably more serious than the loss of mechanical protection for the conductors—the loss of electrical continuity of the conduits and joints, where these are used for earthing purposes. Internal condensation in steel conduits results in an accumulation of rusty moisture at the lower points, leading in time to the breakdown of the rubber insulation of the conductors. Although painting or galvanising may to some extent mitigate or delay the effects of external corrosion, there is no remedy for internal condensation effects, and in industrial installations these may be severe and serious, leading to hold‐ups in production.